Spasticity is a neurological symptom affecting children and adults causing an abnormal increase in muscle tone that occurs when the affected muscle is stretched. Spasticity can occur in neurological disorders that damage the parts of the brain and the nervous system that control voluntary movements. The most common disorders leading to spasticity are cerebral palsy, spinal cord injury, multiple sclerosis, stroke, and traumatic brain injuries, due to a lack of oxygen, physical trauma, haemorrhage, or infection. Some of these injuries can occur at birth and others can occur during adulthood.
The severity of spasticity can range from slight muscle stiffness to deformity and permanent muscle shortening, called contracture. Spasticity often interferes with voluntary movement and with the proper positioning of the body. The presence of spasticity interferes with the accomplishment of activities of daily living such as dressing, eating, and grooming. Spasticity also interferes with mobility, seating and transfers such as moving from the bed to the wheelchair or from sitting to standing. Spasticity also may make it difficult to sit comfortably, or to change positions frequently enough to prevent joint pain and pressure sores. Spasticity in the feet can prevent comfortable fitting of shoes. Severe spasticity may cause painful joint misalignments and limitations in joint movement interfering with hygiene.
Physical, pharmacological and surgical therapies are aimed at decreasing spasticity and restoring motor control. Physical treatments include stretching and positioning to prevent the development of muscle contractures. Pharmacological approaches include oral or intrathecal delivery of drugs targeting the neuromuscular junction of the muscle or the synaptic pathways and nerves innervating the muscle. Local injections of drugs that weaken or paralyze overactive muscle (chemodenervation agents) can be effective for spasticity in isolated muscles. Severe spasticity that cannot be effectively treated with drugs or injections may respond to surgical destruction of some overactive nerves in the spine. Contracture may be treated with serial casting to allow tendons to stretch, or orthopedic surgery if required.
A major problem in the treatment of spasticity is that a sensitive measure of the phenomenon that can be applied at the bedside or in the clinic to make treatment decisions and to judge the effectiveness of treatment does not yet exist. Until now, a variety of different clinical measures have been used to assess spasticity. The current ‘gold standard’ is a 5 point scale (Ashworth Scale) that can only distinguish the presence or absence of spasticity but is not sensitive to its severity. What is more, the scale is subjective, so that the evaluator must ‘judge’ how much resistance is felt when he or she stretches the muscle. Clinicians and researchers agree that this measure is inadequate since it does not discriminate between different types of hypertonicity and does not adequately reflect the severity of spasticity. Furthermore while apparatuses exist for obtaining spasticity measurements that use mechanical components to apply a torque to a joint, they are cumbersome and difficult to adapt to the various types of joints and may create discomfort in the patient.
The identification of the need to have a better (more sensitive and discriminative) measure of spasticity that is easily accessible to the clinician has been apparent for many years.